We must take that the 14 % is volumentric. This is we will use only volumetric measures. From the original solution you can find the quantity of bleach. Original solution: 18 liters * [14 liters of bleach / 100 liters of solution] = 2.52 liters. Now you know that those 2.52 liters shall represent the 10% of the new solution, after having added x liters of water. Then: [2.52 liters of bleach] / [volume of solution] = 10% = 0.1 => volume of solution = 2.52 liters / 0.1 = 25.2 liters of solution. That tells you that you have to add 25.2 liters - 18 liters = 7.2 liters of water. Check that in that case you will have: 2.52 liters of bleach 18 liters of the original solution 7.2 liters of new water added to the original solution. 2.52 liters of bleach / [18 + 7.2] liters of solution = 0.1 = 10%. Then, the answer is: 7.2 liters of water should be added. meaning it would be x - liters of water ( 0% bleach ); ( 18 + x ) * 0.1 = 18 * 0.14 + x * 0 1.8 + 0.1 x = 2.52 + 0 0.1 x = 2.52 - 1.8 0.1 x = 0.72 x = 0.72 : 0.1 x = 7.2 liters Answer: 7.2 liters of water should be added

7.2 is the answer...